Method of reducing copper matte to refined copper.



UNITED STATES PATENT OFFICE.

GEORGE MITCHELL, O1 NACO, ARIZONA TERRITORY.

METHOD OF REDUCING COPPER MATTE TO REFINED COPPER.

SPECIFICATION forming part of Letters Patent No. 7 05,109, dated July22, 1902. Application filed September 5, 1901. Serial No. 74,432. (Nospecimeng,)

T0 (LZZ whom it may concern:

Be it known that I, GEORGE MITCHELL, of Naco, in the county of Cochiseand Territory of Arizona, have invented certain new and usefulImprovements in Methods of Reducing Copper Matte to Refined Copper; andI do hereby declare the following to be a full, clear, and exactdescription of the invention, such as will enable others skilled in theart to which it appertains to make and use the same.

My invention relates to an improved method of reducing copper matte torefined copper. The object of the invention is to facilitate and cheapenthe production of refined copper from sulfid ores.

The following is a description of my improved method of reducing coppermatte to refined copper. Copper matte produced by the Well-known methodof smelting sulfuret ores and containing from forty to sixty per cent.copper (more or less) is charged in a molten condition into acopper-converter provided with a silicious lining and the air-blast onbeing applied is forced into and through the molten matte, with theresult that the iron and sulfur contained in the matte are oxidized andmaintains the charge at a high temperature, causing the iron to attackthe silica lining and convert the iron into silicate of iron or slag,which being lighter than copper floats on the surface of the latter oron the partially-converted charge. After the charge has been blown fromfifteen to thirtyminutes, (more or less,) the time depending on thecharacter of the matte and other conditions, practically all of the ironcontained in the charge will have been converted into slag, and whenthis stage in the operation has been reached and which is called thefirst or slag-forming stage of the process the con verter is turned downand the slag raked off, and then the converter is tilted back into itsupright condition, and the blowing operation is continued and maintaineduntil the charge has been converted into metallic copper,which isindicated to the skilled operator by the color of the flame and thecharacteristics of the sparks that issue and are projected from themouth of the converter. The conversion of matte into metallic copperrequires that the molten charge be furnished with a constant supply ofair to maintain a sufficiently high temperature to insure the rapidoxidation of the impurities contained in the charge. Owing to its lowspecific heat copper will chill and freeze over the inner ends of thetwyers during the blowing of a charge, and unless removed such chilledcopper will so obstruct the twyers and supply of air as to not onlydelay the process, but prevent its successful accomplishment. Henceprovision is made for removing the chilled copper as it forms over theinner ends of the twyers, and this is effected by providing thewind-belt with openings opposite each one of the twyers and furnishingeach one of such openings with a readily-removable plug or stopper orwith a valve or gate that may be quickly opened and closed. A converterprovided with removable stoppers substantially like the one shown inLetters Patent No. 470,644, granted to Pierre Manhes, March 8, 1892, maybe employed, although the well-known Barrel converters now in common usefor convertingcopper maybeemployed. Duringthe blowing of a charge theoperators from time to time insert a drift-bar into the twyers and punchoff any chilled copper that may have formed on their inner ends, andthus insure a continuous supply of air to the molten charge. Lesspunching of the twyers is ordinarily required during the first stage ofthe operation than in the last, due to the fact that as the operationcontinues the heat-producing constituents of the charge graduallydecrease in amount up to the completion of the operation, when all ofthe iron and nearly all of the sulfur and other impurities will havebeen oxidized and eliminated.

The foregoing is a description of the process ordinarily practiced forconverting copper matte into metallic copper, and for the purpose ofclearly distinguishing my invention and improvement .from the presentmethod of reducing metallic copper made by the converter process torefined copper I will first describe the method nowcommonly anduniversally practiced and will then describe my improved method.

After copper matte has been reduced to metallic copper by the converterprocess hereinbefore described the converter is turned down and thecopper is poured into molds and cast into pigs or bars. It is the aim ofthe operation to pour the contents of the converter the instant it hasbeen converted into metallic copper. In the event the blast should bemaintained slightly longer than is necessary to produce metalliccopper-an operation which is designated as overblowing the charge thecontents will contain more or less oxid of copper, and in order toconvert it back to metallic copper a little raw matte and slag andfioor-sweepings are added to the charge,which is reblown a short time toput it in proper condition for pouring.

The converted copper pigs or bars are ordinarily refined by thewell-known Swansea process, which may be briefly described as follows:The pigs or bars of copper are charged into a reverberatory furnace,which is heated by extraneous fuel to melt the pigs or bars and tomaintain the charge in a molten condition until its impurities have beenoxidized and eliminated. To facilitate the process, the molten charge isagitated so as to bring all its particles in contact with theatmospheric air and promote a quick oxidation of the impuritiescontained in the charge. After the charge has been treated in thereverberatory furnace a sufficient length of time to oxidize andeliminate its impurities and which requires from twenty-fourtofortyeight hours (more or less) a portion of the copper will have beentransformed into suboxid of copper, which must be reduced to metalliccopper again; otherwise the copper would be brittle and unfit formanufacturing purposes. This reduction is accomplished by the well-knownprocess of poling, which consists in first covering the molten chargewith charcoal to prevent the access of air thereto and then insertinginto the charge a pole of green wood, which operates to evolve a largevolume of hydrocarbons and other reducing gases and rapidly eliminatesthe excess of oxygen, and after the poling process has been completedthe refined copper is cast into ingots or bars.

I will now describe my improved process, which results in a great savingin time and expense in the reduction of metallic copper to refinedcopper.

After the charge in the converter has been reduced to metallic copperthe air-blast is continued a sufficient length of time to overblow thecharge and oxidize and eliminate all or practically all the sulfur orsulfurousacid gas remaining in the charge and produce suboxid of coppersubstantially equivalent in amount to that which is produced by therefining process as carried on in a reverberatory furnace. The extratime required to overblow the charge will vary slightly with varyingconditions; but at most it will rarely, if ever, exceed five minutes andoftentimes will require not longer than a fraction of a minute. Theoperator can determine by the color and Volume of the flame and sparksescaping from the converter when the charge has been sufficientlyoverblown to insure the production of the proper amount of suboxid inthe charge, which may vary from one to five per cent. (more or less)without seriously interfering or affecting the subsequent refiningoperation. When the molten charge of metallic copper has been overblownin the manner and to the extent set forth,it is poured from theconverter into a ladle, which is moved by an electric crane and itscontents are charged into a reverberatory furnace, when the moltencharge is covered by a layer of charcoal toexclude contact of theatmospheric air therewith, and then the molten mass is poled in themanner already described, and refined and ductile copper is produced.

By overblowing the molten charge of metallic copper in the converter thesame result is obtained in from one to four minutes that requires fromtwenty four to fortyeight hours by the ordinary Swansea process andwhich I have described. In both the object is to eliminate thesulfurous-acid gas and any remaining impurities contained in themetallic copper, and in both this result is attended by the suboxidationof a certain percentage of the mass of metallic copper treated, whichexcess of oxygen must in each case be eliminated by the process ofpoling in order to render the product sufficiently ductile forcommercial use.

By my process I conserve all or nearly all the heat that is stored inthe charge of metallic copper in the converter and utilize the heat inoxidizing and eliminating the impurities, while in the process as nowpracticed such heat is not availed of.

By my process the time, labor, and expense involved in casting themetallic copper into pigs or bars and remelting them again in areverberatory furnace is saved, and, agaimby my process I save the time,labor, and expense that is involved in maintaining the charge of copperin a molten condition and agitating it for a period of from twenty-fourto forty-eight hours, (more or less,) because I attain the same resultby overblowing the charge in the converter.

WVhile I may refine but a single converter charge at a time, I prefer totreat two or more converter charges at a single operation for thefollowing reasons: While the .overblowing of a charge in the convertermay be effected with great certainty and uniformity by a skilledoperator, it might and doubtless would happen that under varyingconditions arising from careless or unskilled workmen or for otherreasons one charge might not be over blown to the required extent toinsure the best results, while another charge might be overblown for alonger period than was reshift,so that all of the charges producedduring the night may be collected and stored in the reverberatoryfurnace in readiness for treatmentin the morning. It will be found thatnotwithstanding the fact that some of the charges so stored in thefurnace may be slightly underblown and others may have been overblownslightly longer than was necessary or desirable the entire mass willcontain sucha proportion of suboxid of copper as will insure itscomplete and satisfactory refining treatment by the poling process.However, in the event the operatorshould find that the accumulatedcharge in the furnace contains too little or too much suboxid of copperfor rapid and economical poling he may bring the charge into propercondition by regulating the condition of the next succeeding convertercharge. If the charge in the furnace contains too little suboxid ofcopper, the next converter charge will be overblown to such a degree asto produce an abnormally-high percentage of suboXid of copper, so thatwhen it is poured into the furnace it will bring the suboxid of theentire mass up to the desired percentage. On the other hand, if it isfound that the contents of the furnace contain too much suboxid ofcopper the next succeeding converter charge may be underblown to such anextent as to contain little or no suboxid of copper, and such chargewhen poured into the furnace will reduce the suboxid to the properpercentage for economical treatment.

After the desired number of converter charges have been poured into thereverberatory furnace the molten mass is covered with charcoal and isthen subjected to the poling process, after which the refined copper isrun into pigs or bars; but the refined metal is preferably cast intoanodes of suitable size and shape to be treated by the well-knownelectrolytic process, as by the elimination of the sulfurous-acid gasand other impurities from the copper. The anodes cast therefrom arehomogeneous and firm in texture and when subjected to the electrolytictreatment do not inj uriously affect the electrolytic bath.

Having fully described my invention, what I claim as new, and desire tosecure by Letters Patent, is-

1. The method of reducing copper matte to refined copper consisting incharging molten copper matte into a converter and blowing air throughthe charge until practically all of the iron in the charge has beenconverted into slag, removing the slag, then reblowing the charge andreducing it to metallic copper and continuing the blowing operationuntil the charge has been overblown suificiently to produce a smallpercentage of suboxid of copper and approximating as nearly as ispossible the amount required to prepare the copper for poling, thencharging the molten con tents of the converter into a reverberatoryfurnace and subjecting it to the po'ling process, substantially as setforth.

2. The method of reducing copper matte to refined copper consisting inblowing copper matte in a converter until practically all the ironcontained in the charge has been transformed into slag, removing theslag, then blowing the remaining charge until it has been reduced tometallic copper and continuing the blowing operation until the metalliccopper has been sufficiently overblown to pro-. duce a small percentageof suboxid of copper and approximating as nearly as is possible theamount required to prepare the copper for poling, punching the twyersduring the blowing of the charge to maintain a constant and practicallyuniform distribution of air throughout the charge; then charging themolten contents of the converter into a reverberatory furnace andsubjecting it to the poling process, and finally casting the prod notinto pigs, bars or anodes, substantially as set forth.

3. The method of reducing copper matte to refined copper consisting inreducing copper matte in a converter to metallic copper containing asmall percentage of suboxid of copper and approximating as nearly as ispossible the amount required to prepare the copper for poling; charginga reverberatory furnace with two or more of such converter charges andsubjecting such mixed and accumulated charges to the poling process, substantially as set forth.

4. The method of reducing copper matte to refined copper consisting inblowing the copper matte in a converter and reducing it tometallic-copper containinga small percentage of suboxid of copper,charging two or more such converter charges into a reverberatoryfurnace, and then adding to such accumulated charge, one or moreadditional converter charges blown to such a predetermined conditionthat when mixed with the accumulated charges they will cause the mass tocontain the desired percentage of suboxid of copper and finallysubjecting the entire charge to the poling process, substantially as setforth.

In testimony whereof I have signed this specification in the presence oftwo subscrib ing witnesses.

GEORGE MITCHELL.

Witnesses:

S. W. FOSTER, GEO. F. DOWNING.

